| | Walla Walla, WA | Mexico, MO | United States |
| Population | 33,765 | 11,592 | 329,725,481 |
| Female Population | 47.3% | 51.8% | 50.5% |
| Male Population | 52.7% | 48.2% | 49.5% |
| Median Age | 36.5 | 37.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 32,522 | 11,517 | 309,327,143 |
| Population - 2000 | 29,686 | 11,320 | 285,036,114 |
| Population - 1990 | 26,478 | 11,290 | 251,960,433 |
| Pop. 2000 to Now | 11.5% | 1.9% | 15.6% |
| Pop. 1990 to Now | 25.0% | 2.1% | 30.8% |
| space4 | | | |
| Population Density | 2,499.1 | 956.9 | 93.4 |
| Land Area | 13.5 | 12.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Walla Walla, WA | Mexico, MO | United States |
| Age 0 to 4 | 4.2% | 7.4% | 5.9% |
| Age 5 to 9 | 5.7% | 5.4% | 6.1% |
| Age 10 to 14 | 6.4% | 5.6% | 6.6% |
| Age 15 to 17 | 3.7% | 4.4% | 3.9% |
| Age 18 to 20 | 7.7% | 2.8% | 4.0% |
| Age 21 to 24 | 6.1% | 4.6% | 5.2% |
| Age 25 to 34 | 13.6% | 16.4% | 13.8% |
| Age 35 to 44 | 12.8% | 11.9% | 12.9% |
| Age 45 to 54 | 11.7% | 10.8% | 12.6% |
| Age 55 to 59 | 5.5% | 7.5% | 6.7% |
| Age 60 to 64 | 4.7% | 6.5% | 6.3% |
| Age 65 to 74 | 9.3% | 9.7% | 9.6% |
| Age 75 to 84 | 4.7% | 4.6% | 4.5% |
| Age 85 and over | 3.7% | 2.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Walla Walla, WA | Mexico, MO | United States |
| White | 66.1% | 84.4% | 59.4% |
| Black | 2.4% | 5.3% | 12.2% |
| Asian | 2.2% | 0.5% | 5.6% |
| Native American | 0.4% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.2% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 4.4% | 6.0% | 3.2% |
| Hispanic | 24.2% | 3.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Walla Walla, WA | Mexico, MO | United States |
| Married Population | 42.9% | 42.3% | 49.8% |
| Currently Married | 39.8% | 41.0% | 48.0% |
| Married but Separated | 3.2% | 1.3% | 1.8% |
| Single Population | 57.1% | 57.7% | 50.2% |
| Never Married | 38.3% | 30.5% | 33.8% |
| Divorced | 12.8% | 19.4% | 10.8% |
| Widowed | 6.0% | 7.8% | 5.6% |
| space5 | | | |
| Household Size | 2.36 | 2.61 | 2.60 |
| Households | 12,583 | 4,345 | 124,010,992 |
| Family Households | 7,151 | 2,719 | 80,755,759 |
| Married couple, w/children | 32.0% | 23.6% | 30.5% |
| Married couple, no children | 41.2% | 41.0% | 42.9% |
| Non Family Households | 5,432 | 1,626 | 43,255,233 |
| Single householder, w/children | 16.8% | 22.3% | 15.8% |
| Single householder, no children | 9.9% | 13.2% | 10.8% |